The optical zones of most contact lenses of either the hard or soft types have smooth regular surfaces on both sides of the lens. Whether spherical, which is the most common surface curvature, or aspheric, the lens surfaces can usually be formed by molding in stationary or spinning molds. When irregularities in one of the surfaces are desired, however, the lens surface must be ground or lathed and then polished to provide the desired surface configuration. Since this must be done manually or by expensive automatic apparatus, cutting and polishing operations of this kind add to the manufacturing costs of lenses having irregularities in their surfaces.
A need has long existed for a less expensive method of making lenses which have surface irregularities, such as grooves and bifocal corrections. The present invention provides a method by which irregular lens surfaces can be formed inexpensively by molding without having to cut the lens surfaces.
The method of the invention comprises a method of making a contact lens of a desired surface configuration which comprises placing a quantity of polymerizable monomer on a mold surface, irradiating monomer on the mold surface with actinic radiation of wavelength and intensity effective to cause said monomer to polymerize, the irradiation of said monomer being through a mask pattern having shadow areas and clear areas, the conditions of irradiation being such that in the regions of the monomer which correspond to the shadow areas of the mask the monomer is polymerized, but at a rate slower than in the regions corresponding to the clear areas of the mask.